Context Value Updating and Multidimensional Neuronal Encoding in the Retrosplenial Cortex
To examine the neuronal dynamics underlying context discrimination and context-value associations in the RSC, Thy1-GCaMP6f transgenic mice were implanted with cranial windows, head-fixed, and pre-trained to reliably run on an air-cushioned spherical treadmill. We then performed two-photon Ca2+ imaging of the expressed genetically encoded calcium indicator GCaMP6f in the dysgranular retrosplenial cortexRSC in layer 2/3 (Fig. 1d-f) while mice performed a contextual discrimination task in a virtual environment. Animals were presented with three different contexts across a series of days, which are defined by the parameters of the virtual environment - including the spatial properties of the linear corridor and the visual pattern present along the length of the corridor. Each context had identical geometry (2-meter-long linear corridor) but unique visual patterns on the virtual corridor walls (Fig. 1c). Following an initial baseline imaging day, a specific context was associated with a water reward, given at a fixed location (180 cm from the beginning of the corridor). Changes in fluorescence (ΔF/F) were imaged and the corresponding position and speed of each animal within the VR environment were recorded. Raw delta F/F and speed values at each position bin along the virtual corridor and at each time bin during ITI for all cells, all trials, and all animals across all days.